Like all food fats, milk fat mainly consists of triglycerides (98%), which are triesters of fatty acids and glycerol. Milk fat is characterized by a large variety of fatty acids (at least ten main different fatty acids) and by a large variety of triglycerides which are combinations of these fatty acids.
Fatty acids with a short chain of 4-10 carbons which are essentially saturated, fatty acids with a long chain of 12-18 carbons which are mainly saturated and mono-unsaturated, and poly-unsaturated fatty acids with a long chain, which are present in an amount of only about 3%, may notably be mentioned; the unsaturated fatty acids are mainly in a <<cis>> configuration, but there are some in a <<trans>> configuration.
These fatty acids mainly have an even number of carbon atoms, but there also exists a small proportion of fatty acids with an odd number of carbon atoms (especially with 15 and 17 carbon atoms).
Furthermore, triglycerides are either triglycerides with a short chain (C36-C42) containing a short chain fatty acid, or triglycerides with a long chain (C44-C54) only containing long chain fatty acids. All these triglycerides are either trisaturated, i.e. they only contain saturated fatty acids, or unsaturated, i.e. they contain one or more unsaturated fatty acids.
Milk fat and food products which are rich in milk fat (such as butter, cream, cheeses . . . ) suffer from a bad nutritional image, because the high saturated fatty acids and the cholesterol contents of this fat discourage their use.
The fatty acid composition of a dairy fat is shown in Table 1.
Upon reading this Table 1, it is observed that the cow milk fatty acid fat contains 65.5% of saturated fatty acids, 31% of mono-unsaturated (<<cis>> and <<trans>>) and about 3.5% of poly-unsaturated (<<cis>> and <<trans>>) fatty acids, these levels being expressed in weight percent over the sum of all the fatty acids reduced to 100%, a sum also called total fatty acids.
Further, this fatty acid composition varies depending on the seasons and on the feeding of milk cows; in spring and summer, milk fat is less saturated, because of feed essentially consisting of fresh grass providing a significant amount of unsaturated fatty acids, whereas in winter, the feed of the cattle (preserved fodder) causes a modification in the dairy fat composition which is enriched with saturated fatty acids.
TABLE 1WinterSummermilkmilkFatty acids (weight %):fatfatAverageC43.73.63.7C62.52.12.3C81.51.21.4C103.12.52.8C10:10.30.30.3C124.03.03.5C1411.89.110.4C14:12.02.02.0C151.21.11.2C1632.424.228.3C16:12.62.62.6C170.80.60.7C17:10.20.30.3C189.713.011.3C18:1 cis18.525.422.0C18:1 trans2.84.83.8C18:2 cis-cis2.12.32.2C18:2 conj. cis − trans0.41.00.7C18:30.30.80.6Sum of saturated fatty acids70.860.565.6Sum of mono-unsaturated26.435.430.9(cis + trans) fatty acidsSum of polyunsaturated2.84.13.5(cis + trans) fatty acids
As the milk material is animal fat, it contains cholesterol (280 mg for 100 g). However, nutritional recommendations recommend that cholesterol food intake be limited to a maximum of 300 mg per day. Consequently, improving the nutritional image of milk fat involves reducing its cholesterol content and its saturated fatty acid content.